Leather treating agent



Patented Apr. 13, 1943 UNITED STATES ATENT orrlce American Cyanamid-Company,

New York,

N. Y., a corporation of Maine No Drawing; ApplicationnAlprili 9, 1941.

Serial No. 387,690

11 Claims.

This invention relates to a new class of leather tanning and bleachingagents, to their preparation and to their application to hides andleather. More specifically it relates to a leather tanning and bleachingagent prepared by reacting a phenol sulfonic acid, an aldehyde and asecondary aliphatic amine.

Condensation products of formaldehyde and certain sulfonated lowerphenols are known and have been used in the bleaching and tanning ofleather. Although some of these compounds have proven satisfactory thereis a demand in the leather art for still better and more 'emcientsynthetic tanning and bleaching agents. I have found that-the reactionproducts of phenol sulfonic acids, including the substituted phenolsulfonic acids, with formaldehyde or other aldehydes and secondaryaliphatic and heterocyclic amines are valuable in the bleaching andtanning of hides, skins and leather and particularly in the bleachingofchrome tanned leather with which they give an exceptionally light, evenshade of a soft, full texture.

I prefer to prepare my new leather tanning and bleaching agents byreacting substantially equi molecular proportions of a phenol sulfonicacid, a secondary amine and formaldehyde and stopping the reactionbefore the product becomes water-insoluble. Ordinarily the reaction iscarried out at elevated temperatures as for example 8098 C. for 0.5-hours. However, the reaction will proceed to the desired stage ofcompletion at room temperatures with a much longer reaction time. Suchproducts prepared at low temperatures are of a lighter color but not soeffective as bleaching agents. In general, it has been found that thefurther the material is condensed the more effective will the product bein the treatment of leather. However, this is qualified by the fact thattemperatures substantially'above 100 C. 'or an unduly prolonged reactionperiod will result in a product of decreased Water solubility andconsequently the reaction time will be governed by this consideration.

As free sulfonic acids are not readily obtainable I' generally preparethem myself by carrying out the necessary sulfonation preliminary to theactual preparation of my new leather treating materials. Although oleum,concentrated H2804, S03, chlorsulfonic acid and other sulfonating agentsmay be employed I prefer to use concentrated H2804 as the sulfonatingagent on account of its ease of handling and availability. A suit ablephenol or substituted phenol is reacted with an excess of concentratedH2504. in the usual manner inorder; to sulfonate the phenol. Thesulfonated mixture, containing'the excess H2SO4 if; desired, is then,reacted with formaldehyde and a secondary aliphatic or heterocyclicamine. Although I may remove the excess sulfuric acid and carryout thecondensation by catalyzing it with an excess of the alkaline secondaryamine this procedure is of no particular advantage and requires theuse-of excess quantities of the amine.

As the presence of sulfuric acid is not harmful to the product, since infact bleaching of chrome tanned leather may take place in acid solutionsI prefer to leave the sulfonating acid in the sulfonated phenol reactionmixture and employ it as catalystfor the condensation. I may,if'desired, react the formaldehyde and secondary amine in a separatereaction vessel before reacting with the sulfonated phenol or I may addthe formaldehyde and, secondary amine simultaneously to the sulfonatedphenol. Ordinarily, however, I add the secondary amine slowly to thesulfonated phenol while holding the mixture at about room temperature,add the formaldehyde slowly with stirring for a short time and then heatthe reaction mixture until the desired stage of reaction has beenreached.

The: product thus obtained contains sulfuric acid remaining from thesulfonation procedure but if desired it may be sold, shipped and usedwithout further treatment. It may however be neutralized, as withammonia, to a desired pH, preferably not over 7.0, and made up into asolution of desired concentration.

My new leather tanning and bleaching agent may be used-With, or toreplace, conventionally employed chrome and vegetable tanning agentsasin th case of the sulfonated phenol-formaldehyde condensation productsheretofore employed for this purpose. My new product is most usefulhowever in the bleaching of chrome tanned leather which ordinarily has apronounced bluish cast and a stiff, hard texture. Such leathers havebeen bleached to a very light even color with an attendant softening ofthe leather. In bleaching chrome tanned leather with my new bleachingagent it is employed in an aqueous solution of 02-40% of activeingredient which may represent from 1-20% by weight of bleaching agentbased on the weight of the leather. The chrome tanned leather is treatedwith such a solution for 0.5-1 hour at temperatures varying from roomtemperature to C. to obtain the desired degree of bleach. Conventionallyemployed fat liquors may be used in the same bath.

Thephenol sulfonic acids which may be rebe substituted with anon-functional group such as an alkyl, alkylol, aryl, hydroxyl, nitro,halogen, cycloalkyl and the like. The essential requirement is simplythat the phenol sulfonic acids have at least one reactive point at whichformaldehyde may react.

Among the various phenol sulfonic acids which may be employed may bementioned specifically unsubstituted phenols such as phenol sulfonicacid, a or 13 naphthol sulfonic acid and the hydroxy anthracene andhydroxyphenanthrene sulfonic acids. Among the substituted phenolsulfonic acids which may be used in my invention are the straight andbranched chain alkyl substituted phenol sulfonic acids such as methyl,ethyl, propyl, isopropyl, butyl, tertiary butyl, amyl, hexyl, octyl,ethyl hexyl, dodecyl and octadecyl sulfonic acids including also thesulfonated commercial ortho and metacresol mixtures; the dialkylsubstituted compounds such as 1.3.5 xylenol sulfonic acid; ortho or metachlor, brom or nitro phenol sulfonic acid; hydroxy diphenyl sulfonicacid; meta dihydroxy benzene sulfonic acid, phenyl phenol sulfonic acidand thelike. It will be understood that by the term phenol sulfonic acidas appears hereinafter and in the claims I intend to include all of theabove mentioned substituted and unsubstituted phenol, naphthol}hydroxyanthracene and hydroxy phenanthracene sulfonic acids and theirequivalents.

Among the various secondary aliphatic and heterocyclic amines which maybe employed in my process are included the aliphatic secondary aminessuch as dimethyl, diethyl, di-n-propyl, diisopropyl, diallyl, methylethyl, methyl-npropyl, methyl butyl, methyl dodecyl, methyl oleyl, ethylbutyl, dimethanol, diethanol, 5,5- dicyano diethyl amine and theheterocyclic secondary amines such as dicyclohexyl amine,

piperazine, triethylene tetramine and morpholine.

The preparation of my compounds will now be illustrated in connectionwith the following specific examples which are given to illustrate someof the more specific details of the preparation but are not intended tobe construed as in limitation thereof.

Example 1 196 parts by weight (2 moles) of H2804 were added slowly withstirring to 164 parts by weight (1 mole) of o-amyl phenol and thetemperature of the mixture allowed to rise to 60 C. After standing 2hours at a temperature of 60 C, 100 partsby weight of water was addedand the mixture cooled to room temperature. 8'7 parts by weight (1 mole)of morpholine was then added and the mixture again cooled to roomtemperature. 1 mole of formaldehyde in the form of a 37% by weightsolution was added to the reaction mixture slowly with stirring and thestirring continued for 2 hours at room temperature. The temperature ofthe mixture was then raised a 50% stock solution in 50% ethanol.

to -100 C. and held at this temperature for 1 hour.

One-half of the material prepared as above described was neutralizedwith ammonia and made up with 50% alcohol to a solution containing 50%solids. A chrome tan leather was effectively bleached with thismaterial.

The remaining half of the reaction mixture described was heated 4 hoursat 95-100 C. During this further condensation the solubility of thematerial decreased and on cooling a water soluble, gum-like materialseparated out. The resin was removed mechanically and made up to Thisproduct, when used as a 10% water solution, was an effective syntan andbleached chrome tanned leather to a light, even shade without raisingthe grain.

Example 2 196 parts by weight of concentrated HzSOq. was added slowlyover a period of 0.5 hour with stirring to 164 parts by weight of o-amylphenol. The temperature of the reaction mixture was allowed to rise to60 C. and was maintained at this temperature for 2 hours after theaddition of sulfuric acid. parts by weight of water was added withcooling to room temperature. parts by weight of diethanolamine was thenadded dropwise to the above mixture while holding the temperature atabout 25 C. 30 parts by weight of CI-IzO in the form of a 37% by weightsolution (81.1 parts by weight) was added dropwise with stirring and thestirring continued for hour after all the formaldehyde was in. Themixture was then heated on a steam bath for 1 hour, and 200 parts byweight of water added. The material was then adjusted to a pH of 6.5-7.0with ammonia and made up to 1200 parts by weight with watercorresponding to a 30% solution of the syntan. This material also provedto be a good bleaching agent for both chrome and vegetable tannedleathers.

Example 3 1 mole of o-cresol was sulfonated with 2 moles of concentratedsulfuric acid as described in the preceding examples. 1 mole ofmorpholine and 1 mole of formaldehyde were condensed in a separatereaction vessel for a. period of about hour at a temperature of 90 C.The resulting syrup was then added to the sulfonation mixture over aperiod of 0.5 hour with stirring at room temperature. The temperature ofthe mixture was then raised to 95 C. and held at this temperature forabout 1 hour. The contents of the reaction vessel were then neutralizedand dissolved in water with the aid of a small amount of ethyl alcohol.If desired the condensation may be allowed to take place at roomtemperatures but a correspondingly longer time will be required for thereaction to reach the desired stage of completion. Such productsprepared at lower temperatures are lighter in color.

An effective bleaching agent for chrome and vegetable tanned leatherswas also prepared exactly as described above except that a commercialmixture of ortho and meta cresols was employed in place of the pureo-cresol. A leather bleaching agent was also prepared as above describedwith 1 mole of diethanolamine instead of morpholine. The productsdescribed were in general syrupy masses soluble in water and varying incolor from a very light tan to dark brown and may be used either astanning agents with or without conventional chrome or vegetable tans toyield soft and well-filled leather, or they may be very effectivelyemployed as bleaching agents to give light, even-colored leathers.

E sample 4 1 mole of tertiary butyl phenol Was sulfonated with 2 molesof sulfuric acid as described in Example l and diluted with 100 parts ofwater and cooled to room temperature. 1 mole of5,,8-dicyano-diethylamine was dissolved in 1 mole of an aqueous solutionof formaldehyde with stirring and then added to the sulfonated tertiarybutyl phenol-sulfuric acid mixture. The mixture was stirred minutes at60 C., refluxed 15 minutes and then cooled, neutralized with 200 partsby weight of NH4OH and made up to a so-' lution containing by weight ofthe syntan based on an assumed molecular weight of 365. This materialwas also a very satisfactory bleach for chrome and vegetable tannedleathers.

What I claim is:

1. A process of preparing leather tanning and bleaching agents whichcomprises reacting in acid media at-temperatures not in excess of 100 C.for not more than 5 hours a phenol sulfonic acid having at least onereactive ortho or para position in the nucleus, formaldehyde and asecondary aliphatic amine and stopping the reaction before the productbecomes water-insoluble.

2. A process of preparing leather tanning and bleaching agents whichcomprises reacting at temperatures not in excess of 100 C. for not morethan 5 hours phenol sulfonic acid, formaldehyde and a secondaryaliphatic amine in the presence of sulfuric acid and stopping thereaction before the product becomes water-insoluble.

3. A process of preparing leather tanning and bleaching agents whichcomprises reacting at temperatures not in excess of 100 C. for not morethan 5 hours an alkyl phenol sulfonic acid having at least one reactiveortho or para position in the nucleus, formaldehyde and a secondaryaliphatic amine in the presence of sulfuric acid and stopping thereaction'before the product becomes water-insoluble.

4. A process of preparing leather tanning and bleaching agents whichcomprises reacting at temperatures not in excess of 100 C. for not morethan 5 hours butyl phenol sulfonic acid having at least one reactiveortho or para position in the nucleus, formaldehyde and a secondaryaliphatic amine in the presence of sulfuric acid and stopping thereaction before the product becomes water-insoluble.

5. A process of preparing leather tanning and bleaching agents whichcomprises reacting at temperatures not in excess of C. for not more than5 hours tertiary butyl phenol sulfonic acid, formaldehyde anddiethanolamine in the presence of sulfuric acid and stopping thereaction before the product becomes water-insoluble.

6. A process of preparing leather tanning and bleaching agents whichcomprises reacting at temperatures not in excess of 100 C. for not morethan 5 hours tertiary butyl phenol sulfonic acid, formaldehyde and3,;9-dicyanodiethylamine in the presence of sulfuric acid and stoppingthe reaction before the product becomes water-insoluble.

7. A leather tanning and bleaching agent which comprises theWater-soluble reaction product obtained by heating at temperatures notin excess of 100 C. for not more than 5 hours in acid media a phenolsulfonic acid having at least one reactive ortho or para position in thenucleus, an aldehyde and a secondary aliphatic amine.

8. A leather tanning and bleaching agent which comprises thewater-soluble reaction prodnot obtained by heating at temperatures notin excess of 100 C. for not more than 5 hours in acid media phenolsulfonic acid, formaldehyde and a secondary aliphatic amine.

9. A leather tanning and bleaching agent which comprises thewater-soluble reaction product obtained by heating at temperatures notin excess of 100 C. for not more than 5 hours in acid media an alkylphenol sulfonic acid having at least one reactive ortho or para positionin the nucleus, formaldehyde and a secondary aliphatic amine.

10. A leather tanning and bleaching agent which comprises thewater-soluble reactionproduct obtained by heating at temperatures not inexcess of 100 C. for not more than 5 hours butyl phenol sulfonic acidhaving at least one reactive ortho or para position in the nucleus,formaldehyde and diethanolamine in the presence of sulfuric acid andstopping the reaction before the product becomes water-insoluble.

11. A leather tanning and bleaching agent which comprises thewater-soluble reaction prodnot obtained by heating at temperatures notin excess of 100 C. for not more than 5 hours butyl phenol sulfonic acidhaving at least one reactive ortho or para position in the nucleus,formaldehyde and B,fi-dicyanodiethylamine in the presence of sulfuricacid and stopping the reaction before the product becomeswater-insoluble.

MALCOLM J. REIDER.

